(1) deployment of well-washed rocks in a pristine stream for 40 days to allow colonization of macro invertebrates;

(2) retrieval of those rocks that are then placed in 36 flow-thru “streams” at the Aquatic Experimental Lab (USGS-Fort Collins);

(3) manipulation of metal concentrations in the “streams;"

(4) daily collection of emergent adults during the 30-day experiment;

(5) multiple measurements of water quality (temperature, pH, dissolved major and minor ions, and DOC) during the experiment; and, at its conclusion,

(6) identification and counting of larval invertebrates in each stream. Each experiment simultaneously considers impacts of individual metals and binary metal mixtures on the health of the invertebrate communities.

Using Zn as a reference point and the experimental design of our previous Cd-Zn experiment, our plan is to conduct an experiment with Cd, Cu, Zn, Cu+Zn, and Cd+Cu+Zn in year 1; Cu, Ni, Zn, Ni+Zn, Cu+Ni+Zn in year 2, and Co, Cu, Ni, Zn, Co+Zn, Co+Cu+Ni+Zn in year 3. Results and interpretation of the experiments will be presented at national meetings and in journal articles.